Quoted From The Official Sub-Mariner Thread:
He is listed as being class 100 strength that deteriorates as he dries out but he has that suit that can keep him wet.
He is pretty invunerable as is but also has his Atlantean armor from Neptune which bolsters his invunerability and strength.
He also has Neptunes Trident which allows him to control water, create water elementals, earthquakes, tidal waves, rain, fog etcetera.
He has a limited ability to control marine life, sonar and can create electic blasts light an electric eel.
He can also absorb other forms of energy and use them as electric blasts. He has that horn that gives him total control over all marine life.
He can make mental projections and the Sword of Kamuu is as powerful as the Ebony Blade and can negate any magic even that of Dr. Strange, it also make him stronger and enchanted.
He can fly and has heightened sences and reflexes.